Conventionally, Japanese Patent Laid-Open (A) 8-68953 proposes an eyepiece lens system having a long eye-relief (the distance between the pupil and the lens surface of the eyepiece lens system which is closest to that pupil. This conventional eyepiece lens system comprises, from the pupil side and proceeding toward the object side, a first-lens unit having a positive refractive power, a second lens unit having a positive refractive power, and a third lens unit having a positive refractive power.
However, the eyepiece lens system disclosed in the above Patent Laid-Open document has a problem in that both a field curvature and a distortion are not corrected with a good balance.